Actually, given the current state of affairs, the Xeons tend to be the best choice, but it depends on budget. I'd suggest Dual MPs only if you really don't have the cash to go Xeon, because Xeons will probably give you very good peformance in video editing using premiere and After effects - even more so if you consider the new PC-DL, but we'll get to that later.
Dual MPs tend to have less efficient chipsets. Also, because of the arrival of the (probably very fast, but we haven't seen any reviews yet) of the 3.06Ghz Xeon with 1MB L3 cache (1.5MB L2+L3 cache), the whole Xeon line is costing less. It's still more expensive than the MPs, though. The motherboards aren't cheap either.
Now moving on to the Canterwood-based ASUS PC-DL: it looks awesome. Canterwood's memory controller is more up-to-date, as are its features. It will probably support non-ECC memory as well, which will make the platform that much cheaper. It sports AGP 8x, dual channel ddr333, and S-ATA. Looks like a powerhouse - and because it's based on Canterwood, it might be less expensive than the usual Xeon mobos. Consider, however, that it might also be limited to 4GB system memory, unlike typical Xeon mobos - but that might not be an issue to a typical dual-cpu enthusiast for a few years...
So if you're considering dual processors (or are just enthusastic about this idea!

), I'd say wait for the PC-DL to come out. Right now, dual Opterons are not a good choice for you, because their performance is somewhat limited in typical 32-bit workstation tasks, like THG itself concluded.
<font color=red><b>M</b></font color=red>ephistopheles